Stachylysin may be a cause of hemorrhaging in humans exposed to Stachybotrys chartarum

Abstract

Stachybotrys chartarum is a toxigenic fungus that has been associated with human health concerns such as nasal bleeding in adults and pulmonary hemosiderosis (PH) in infants. Seven of eight strains of S. chartarum isolated from homes of infants with PH in Cleveland, Ohio, and the strain from the lung of an infant with PH in Texas produced stachylysin in tryptic soy broth (TSB), whereas only one out of eight strains isolated from control homes produced stachylysin. However, all strains produced stachylysin when grown on TSB with 0.7% sheep's blood. When stachylysin was injected into Lumbricus terrestis, the erythrocruorin hemoglobin (absorbance peaks at 280 and 415 nm) was released, resulting in a lethal effect. These results support the hypothesis that stachylysin may be one agent responsible for hemorrhaging in humans.

FIG. 1.

(A) Purified stachylysin was subjected to native protein electrophoresis with a 4 to 15% Tris-HCl gel stained with silver (using the Bio-Rad Silver Stain Plus kit). (B) The native stachylysin band did not stain initially with this silver reagent used for panel A and was treated by oxidizing with 1% hydrogen peroxide for 15 min. The gel cleared with 3 mM potassium dichromate in 3 mM nitric acid and then restained.

FIG. 2.

Purified stachylysin was subjected to native protein electrophoresis using a 4 to 15% Tris-HCl gel. Half of the gel was then silver stained (using the Bio-Rad Silver Stain Plus kit) (A), and the other half was placed on SBA and then photographed at 24 h (B) and 48 h (C).

FIG. 3.

Appearance of reddish excretions from L. terrestis 6 h after injection with 100 μl of concentrate from strain 58-06 grown for 7 days in TSB.

FIG. 4.

Appearance of a dorsal vessel of L. terrestis 6 h after injection with 100 μl of concentrate from S. chartarum strain 58-06 grown for 7 days in TSB (left) and of an untreated earthworm (right). The arrows indicate possible aneurisms. The worms are back-lighted to reveal internal structures.

FIG. 5.

Spectrum of excretions from L. terrestis treated with stachylysin after removal of the debris by centrifugation. The supernatant was analyzed spectrophotometrically by scanning from 200 to 600 nm with a Beckman DU-600 spectrophotometer. Peaks at 280 and 415 are characteristic of the earthworm hemoglobin.